Well...for most Glock parts, you can head on to Final Option. They have an intensive list of parts available like springs, connectors, barrels (from time to time, availability is not a constant thing), sights etc. I bought my Pearce grip and Trijicon night sights from them.
For tactical lights, there's S.O.E. with their selection of SureFire and other brands of weapons lights. Be sure to check their tactical gear too, they carry both BlackHawk and some Fobus IWBs now (not the paddle type, the good Fobus designs!)
For lasers, try Jethro or Twin Pines.
All are located at the basement level of Makati Cinema Square.